1. Field of the Invention
The present invention generally relates to a motor, and more particularly to a motor that rotatably drives discs, such as, for example, a CD-ROM, a DVD-ROM and the like. The present invention also relates to a method for manufacturing a motor for rotatably driving discs.
2. Description of Related Art
In conventional motors, when a rotator such as a turntable is affixed to a rotor shaft, the rotor shaft is engaged with the turntable by a running fit method. In the running fit method, an adhesive is filled in a gap between the rotor shaft and a central bore of the turntable to thereby affix the turntable to the rotor shaft. More specifically, when the turntable is affixed to the rotor shaft, the adhesive is coated on an internal surface of the bore of the turntable, and the rotor shaft is inserted in the bore of the turntable. However, in the structure that uses a running fit, the turntable needs to be fixed at a specified portion with respect to the rotor shaft until the adhesive hardens. As a result, the production efficiency is lowered and the plane oscillation characteristic becomes unstable.
Also, since the turntable coated with the adhesive is inserted over the rotor shaft, the adhesive may adhere to areas of the rotor shaft where bonding by the adhesive is not required. In the case of a spindle motor for CDs, a core adjusting ring is spring-loaded about the rotor shaft and moves along the rotor shaft with respect to the turntable. In order to secure the movement of the core adjusting ring, the adhesive adhered to the rotor shaft must be completely removed from the rotor shaft. Accordingly, the work efficiency is lowered due to the cleaning work that is required to remove the adhesive from the rotor.
Moreover, the adhesive that is coated on the internal surface of the bore of the turntable is scraped off by the rotor shaft when the rotor shaft is inserted in the bore of the turntable. As a result, only a small amount of the adhesive remains in the gap between the bore of the turntable and the rotor shaft, and therefore problems occur in that a sufficient bonding strength cannot be obtained. Also, variations would likely occur in the bonding strength.
Moreover, if the turntable is affixed to the rotor shaft by a pressure-insertion to obtain a sufficient bonding strength, and the pressure is excessive, the thrust bearing provided under the rotor shaft may deform. This results in problems, such as, deterioration of the motor characteristics.
The present invention has been made to solve the problems of the prior art described above. It is an object of the present invention to provide a motor having an engaging section between a rotor shaft and a rotator with a step-like structure, which allows the rotator and the rotor shaft to be securely affixed to each other by a pressure-insertion and an adhesive.
In accordance with an embodiment of the present invention, a motor has a rotatably supported rotor shaft and a rotator that rotates together with the rotor shaft in a unit. The rotator includes a shaft insertion section that has an internal peripheral surface and a specified length in an axial direction in which the rotor shaft is inserted. In one aspect of the embodiment of the present invention, the internal peripheral surface has a first internal peripheral surface of a small diameter and a second internal peripheral surface having a diameter slightly greater than that of the first internal peripheral surface. In another aspect of the embodiment of the present invention, the first internal peripheral surface engages the rotor shaft, and the second internal peripheral surface is slightly spaced a distance from the rotor shaft, such that a gap is created between the second internal peripheral surface and the rotor shaft. In another aspect of the embodiment of the present invention, the rotor shaft is pressure-inserted in the first internal peripheral surface to be affixed to the rotator, and an adhesive is filled in the gap between the second internal peripheral surface and the rotor shaft to affix the second internal surface to the rotator.
As a result, the rotator is maintained at a fixed position with respect to the rotor shaft after the rotator is inserted over the rotor shaft until succeeding steps without an extra tool to support and retain the rotor shaft with respect to the rotator. Also, if the rotator is temporarily affixed to the rotor shaft, the position of the rotator can be readjusted after the rotator is pressure-inserted over the rotor shaft. Also, an adhesive can be coated after the rotator is inserted over the rotor shaft. As a result, the adhesive is not scraped off when the rotator is pressure-inserted over the rotor shaft, the adhesive does not stain the rotor shaft, and variations in the adhesive coat do not occur.
In accordance with another embodiment of the present invention, a lid member may be pressure-inserted over the rotor shaft on an opposite side of the first internal peripheral surface with the second internal peripheral surface being interposed between the first internal peripheral surface and the lid. As a result, the gap is covered by the lid member. Also, the lid member can help maintaining a high bonding strength for a longer period when an anaerobic adhesive is used.
In accordance with another embodiment of the present invention, the rotator may be a turntable on which a disc is mounted, the insertion section may be formed on the turntable. As a result, the turntable for driving a disc can be affixed to the rotor shaft with a sufficient bonding strength.
Moreover, in accordance with another embodiment of the present invention, the rotor shaft is pressure-inserted in the rotator under a relatively light pressure. The rotator does not move with respect to the rotor shaft after the rotor shaft is pressure-inserted in the rotator until a succeeding step, such that the rotator and the rotor shaft are temporarily, readily connected to each other, and the position of the rotator can be readjusted after the rotator is pressure-inserted over the rotor shaft.
Furthermore, in accordance with another embodiment of the present invention, the rotator is not limited to a turntable, but also includes a rotor case.
In accordance with an embodiment of the present invention, a method for manufacturing a motor comprises the steps of providing a rotator with a stepped shaft insertion section that has a first bore of a first diameter smaller than a diameter of the rotor shaft and a second bore having a second diameter greater than the first diameter of the first bore such that a gap is created between the second bore and the rotor shaft. The rotor shaft is pressure-inserted in the first bore, and then, an adhesive is filled in the gap between the second bore and the rotor shaft. As a result, the adhesive does not stain the rotor shaft, and variations in the adhesive coat do not occur. The method of the embodiment of the present invention substantially improves the production efficiency.
Other features and advantages of the invention will be apparent from the following detailed description, taken in conjunction with the accompanying drawings that illustrate, by way of example, various features of embodiments of the invention.